Use Polyethylene tubing only for systems with working pressure of 30 psig
or less. Provide flame-resistant, multiple polyethylene tubing in
flame-resistant protective sheath with Mylar barrier, or unsheathed
polyethylene tubing in rigid metal, intermediate metal, or electrical
metallic tubing conduit for areas where tubing is exposed. Single,
unsheathed, flame-resistant polyethylene tubing may be used where concealed
in walls or above ceilings and within control panels. Do not provide
polyethylene tubing for [systems indicated as critical and] smoke removal
systems. Provide polyethylene tubing only for working pressures of 30 psig
or less. Number each tube in sheathing each two feet minimum. Permanently
identify unsheathed tubing at each end. Provide compression or brass
barbed push-on type fittings.Fittings shall be compression or barbed
push-on type.
Extruded seamless polyethylene tubing shall conform to the
following:
a.
Minimum Burst Pressure Requirements: 100 psig 690 kPA at 75
degrees F 24 degrees C to 25 psig 172 kPa at 150 degrees F 66
degrees C.
b.
Stress Crack Resistance:
ASTM D 1693, 200 hours minimum.
c.
Tensile Strength (Minimum): ASTM D 638, 7583 kPa 1100 psi.
d.
Flow Rate (Average):
ASTM D 1238, 0.30 decigram per minute.
e.
Density (Average):
ASTM D 792, 920 kg/m3 57.5 pounds per cubic
feet.
f.
Burn rate:
ASTM D 635
**************************************************************************
NOTE: Delete the following section if variable
frequency motor drives are not used in this
specification.
**************************************************************************
2.8
VARIABLE FREQUENCY MOTOR DRIVES
The variable frequency drive (VFD) shall convert 240 or 460 volt (+/- 10%),
three phase, 60 hertz (+/- 2Hz), utility grade power to adjustable
voltage/frequency, three phase, AC power for stepless motor control from 5%
to 105% of base speed.
2.8.1
Description
The variable frequency drive (VFD) shall produce an adjustable AC voltage/
frequency output for complete motor speed control. The VFD must meet all
of the following criteria:
a.
The VFD shall use sine coded Pulse Width Modulation (PWM)
technology. The sine coded PWM calculations are performed by the
VFD microprocessor.
b.
The VFD shall use Insulated Gate Bipolar Transistors (IGBT)
transistors for the inverter's three phase output.
c.
The VFD shall use a three phase diode bridge converter to charge
the VFD constant voltage capacitor buss.
SECTION 15910N
Page 52
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